1. Field of the Invention
The present invention relates to a vacuum circuit breaker, and more particularly, to an interlock apparatus for preventing (prohibiting) a main body of the vacuum circuit breaker from being drawn out or drawn in when the ground switch of the vacuum circuit breaker is located at a ground position.
2. Description of the Conventional Art
Typically, a vacuum circuit breaker is an electric power device mounted in a circuit breaker chamber of the switchgear (i.e., in other words electric power distributing board) to connect a primary side (electric power receiving side) circuit with a secondary side (electric power distributing side) circuit, thereby allowing a normal current conduction to supply electric power to load-side devices in normal times. Also, the vacuum circuit breaker is an electric power device for breaking the electric circuit to protect electric power lines and load devices when a fault current such as a short circuit current occurs, and handling high voltages above several thousand kilovolts or ultra-high voltages above several tens of thousand kilovolts.
In addition, the vacuum circuit breaker is configured with a structure that a circuit breaker main body can be moved to a drawing-in position where it is connected to the electric circuit and a drawing-out position where it is separated from the circuit, within the circuit breaker chamber. In other words, it is configured such a manner that the circuit breaker main body can be drawn out with only simple manipulation when performing the maintenance of the vacuum circuit breaker, and also the circuit breaker main body can be simply moved to the drawing-in position when completing the maintenance. For the detailed construction and operation for drawing in or out such a drawing-out type vacuum circuit breaker, it may be possible to refer to the disclosure of Korean Grant Patent No. 10-0324492 (Title of the invention: Device for transferring movable unit of circuit breaker) which is filed and registered by the applicant of the present invention.
On the other hand, the operation for discharging a current charged on the secondary side (load-side) conduction portion on the circuit is necessarily required to protect an operator from the safety accidents of electric shock when implementing the maintenance of the circuit breaker main body. The technologies for discharging the charged current have been developed from the prior art in which a user directly discharges the current charged on each phase conductive portion of the three-phases alternate current using the ground rod to a technology in which the charged three-phases currents can be discharged at the same time by using an ground switch. Accordingly, while discharging the ground, it is used a ground discharging method using an ground switch capable of minimizing a power failure time during the maintenance and securing the user's safety, and the ratio of switchgears (distributing board panels) using such a technology has been increased. For the construction and operation of an ground switch for providing a concurrent three-phases automatic grounding function disclosed herein, it may be possible to refer to the disclosure of Korean Grant Patent No. 10-0505053 (Title of the invention: Toggle-type ground switch for a multi pole circuit breaker) which is filed and registered by the applicant of the present invention.
There is a function that should be necessarily secured when applying such a structure, which is a function for preventing the circuit breaker main body from being driven at the ON position by moving it to the drawing-in position in a state that an ground switch for discharging secondary-side charged current in a circuit (namely, at the ground position) is on. If electric power source is applied to the circuit when the circuit breaker is on in a state that the secondary-side (load-side) circuit is connected to the ground, then it may result in a ground fault, thereby causing enormous damage. As a result, it is required an interlock apparatus in which the ON manipulation of the ground switch and the drawing-in position movement manipulation of the circuit breaker are interlocked to prohibit (prevent) the operation.